The Guianan Gnatcatcher is described as a little-known canopy insectivore. A 2005 taxonomic paper examined the nominate form in French Guiana, Suriname, Guyana, and northern Amazonas, Brazil.
In the P. g. guianensis specimens, the throat is whiter than the breast. Males have a narrow white eye-ring; females are whiter overall and have a more conspicuous eye-ring and a narrow white supercilium.
The 2005 paper describes this species as a poorly known canopy insectivore. At that time, natural-history information and specimens were limited.
An extinction-risk assessment has not been added yet.